The DA, out for the blood of grafters, goes on the radio naming a handful of prominent people he believes are top corrupting criminals in the city. He's going to indict one of them in his latest case, the 13th, tomorrow. Needless to say, he's murdered that night. As is often the case in 1930s and '40s mysteries, newspapermen do the sleuthing.
This nicely paced mystery is easy to solve if you've seen enough of them. There are many here at IA. There's good banter early on, but I had trouble in discerning some of it. Some was too anachronistic for me. Of the mysteries that I've seen, I believe this was the first one in which a newspaper man is killed during an investigation. When a good guy was murdered, it's always been a cop or a private detective.
A newspaperman also dies during an investigation in http://www.archive.org/details/Murder_with_Pictures_1936"
rel="nofollow">Murder with Pictures
I downloaded the 589MB AVI file. Video quality was good. The audio was mostly Ok.